"It is frankly hard to believe that people thought a Trump candidacy was funny, but there was such a time," Oliver said.

The host then showed video of himself guest-hosting "The Daily Show" three years ago and responding to news that Trump was considering a run for president in 2016.

"Do it. Do it," Oliver said back then on "The Daily Show." "I will personally write you a campaign check now on behalf of this country, which does not want you to be president but which badly wants you to run."

The "Last Week Tonight" audience responded to the clip disapprovingly, and Oliver said, "In my defense, I have no defense for that and was hoping to think of one before finishing this sentence, and oh s---, it's over."

Oliver continued, "I want to believe that America will reject Donald Trump, that our innate sense of decency will kick in like some sort of moral auto-pilot, but I have been spectacularly wrong before."

Then he dug up yet another "Daily Show" clip from eight years ago in which he said the Chicago Cubs would never win a World Series — which, of course, also happened in 2016.

"I'm an idiot. But that clearly shows no outcome is certain, so if you are thinking you don't have to show up to vote on Tuesday because there is no way the impossible could happen, take it from somebody who has learned from painful experience: You are wrong about that," Oliver said.